1. Field of the Invention
This invention relates to an erasing device with the function of erasing information from a recording medium such as a floppy disk which is provided with tracks on which images exclusively are recorded and tracks on which sound exclusively is recorded, with the two kinds of information to be mixed as in a still video standard.
2. Description of the Related Art
FIG. 3 shows a flowchart of the conventional
An example of a conventional erasing procedure in a still video recording and reproducing apparatus provided with the function of erasing is in the flowchart shown in FIG. 3.
When erasing is performed, the "ERASE STANDBY" mode is first selected. Next, when the reproduction mode has not been selected, the reproduction mode is selected to reproduce an image in the track accessed by the head.
When the switch marked "ERASE ON" is pressed after a picture to be erased is recognized by the monitor, erasing of one track is performed.
Such an erasing method is described in U.S. Pat. Application Ser. No. 033,339, which is an application assigned to the assignee of this invention.
The method of recording audio signals which is defined on the basis of the still video standard is described below.
The time base of an audio signal is compressed so that the frequency band of the audio signal is raised to the band of a video signal, and is then recorded by using the same recording system as that used for the video signal. When the time needed to record a compressed audio signal exceeds the recording time for a single track, the audio signal can be recorded on a plurality of tracks.
A simple description will now be given of a recording format for an audio signal.
FIG. 5 shows an example of an audio track recorded on a track formed in a magnetic sheet. The audio track is divided into four sectors, S.sub.A to S.sub.D, the format of each of the sectors is shown in FIG. 6. A start signal of an audio sector is indicated by a start flag SF recorded in the start position in one sector, and then the compression ratio of the time base of the audio signal, the address of the track of the video signal to which the audio signal corresponds, and, when the audio signal is continuously recorded in a plurality of tracks, the address of the track where the audio signal starts and the addresses of the following tracks where the audio signal is recorded are recorded as a control code for reproducing the audio signal track. When the audio signal is continuously recorded on a plurality of tracks, the tracks are considered as a single block which is referred to as one audio sequence hereinafter. When the audio signal is recorded on a single track, the track is also referred to as one audio sequence hereinafter.
When an audio signal recorded on a disk on which tracks of audio signals and tracks of video signals are mixed is erased in accordance with the conventional procedure shown in FIG. 3, then since the audio signal to be erased cannot be previously recognized, the procedure has a problem with respect to erroneous erasing.
In the above-described audio format, since an audio sequence can be controlled by the control code, it is unnecessary to recognize the track on which the audio signal to be erased is recorded. Therefore, a conventional erasing device has a problem in that, if the track containing the audio signal to be erased is not known beforehand, the audio signal cannot be easily erased.
The conventional erasing device also has a problem in that, when it is desired to erase only the video signal, then it must be determined whether the video signal is in an audio sequence or is unrelated to any audio signal. Otherwise, erroneous erasing may be made in some cases.
In addition, when the video signal corresponding to an audio signal is erased, it is necessary to change the contents assigned by the control code on the track of the audio signal.